linux-kernel - Re: WARNING in md

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Date:   Tue, 20 Oct 2020 22:28:36 -0700
From:   Song Liu <song@...nel.org>
To:     "Dae R. Jeong" <dae.r.jeong@...st.ac.kr>
Cc:     yjkwon@...st.ac.kr, linux-raid <linux-raid@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: WARNING in md_ioctl

On Mon, Oct 19, 2020 at 12:03 AM Dae R. Jeong <dae.r.jeong@...st.ac.kr> wrote:
>
> > diff --git i/drivers/md/md.c w/drivers/md/md.c
> > index 6072782070230..49442a3f4605b 100644
> > --- i/drivers/md/md.c
> > +++ w/drivers/md/md.c
> > @@ -7591,8 +7591,10 @@ static int md_ioctl(struct block_device *bdev,
> > fmode_t mode,
> >                         err = -EBUSY;
> >                         goto out;
> >                 }
> > -               WARN_ON_ONCE(test_bit(MD_CLOSING, &mddev->flags));
> > -               set_bit(MD_CLOSING, &mddev->flags);
> > +               if (test_and_set_bit(MD_CLOSING, &mddev->flags)) {
> > +                       err = -EBUSY;
> > +                       goto out;
> > +               }
> >                 did_set_md_closing = true;
> >                 mutex_unlock(&mddev->open_mutex);
> >                 sync_blockdev(bdev);
> >
> > Could you please test whether this fixes the issue?
>
> Since &mddev->open_mutex is held when testing a bit of mddev->flags, I
> modified the code just a little bit by putting mutex_unlock() as
> belows.

Good catch! The fix looks good. Would you like to submit a patch for it?

Thanks,
Song